1. Field of the Invention
The present invention relates generally to autonomous vehicles and controlling method thereof, and more particularly, to an autonomous vehicle which travels/stops parallel to a wall and a controlling method thereof.
2. Description of the Related Art
Autonomous vehicles have been extensively studied in recent years. There is known for example an autonomous vehicle which waxes all over a floor by repeating a straightforward movement and a U-turn. An example of a method of controlling such an autonomous vehicle is to control a straightforward and turning movement by detecting the number of rotation of its wheels. Such an autonomous vehicle requires improvements in the precision of straightforward movement and the rotation movement as the vehicle makes a U-turn. The autonomous vehicle using the controlling method is not necessarily capable of accurate operation if its wheels slip on a floor. An autonomous vehicle disclosed by Japanese Patent Laying-Open No. 3-160507 is directed to a solution to this problem. This conventional autonomous vehicle measures the distance between a wall and itself using a distance measurement sensor to produce the position and direction of itself and travels parallel to the wall.
Such an autonomous vehicle which moves only based on the distance information between the wall and itself cannot accurately detect the direction of the vehicle body. Therefore, while the vehicle generally travels along a wall, the direction of the vehicle body is not always exactly parallel to the wall, and does not necessarily stop exactly parallel to the wall. If the vehicle is to wax all over a floor as described above, the vehicle repeat the operation of crossing the floor, making a 180.degree. turn and proceeding parallel to the previous course in the opposite direction. Unless the direction of the body is parallel to the wall when one straightforward travel completes, the operation during such traveling will be instable.
Furthermore, in order to thoroughly wax the area along the wall, the initial position of the body should be strictly specified. Depending upon the initial position of the body, the unsteadiness of the body during traveling could be large.